Porous Mn-based mullite SmMn2O5 was synthesized by the in-situ dismutation of solid state Mn3+ in bulk SmMnO3 perovskite to catalytic oxidation of benzene and chrolobenznen. The physicochemical property of catalyst was acquired by XRD, SEM, N-2 adsorption-desorption, XPS, O-2-TPD and H-2-TPR. Compared with that of bulk SmMnO3 and bulk SmMn2O5, the porous SmMn2O5 mullite (SmMn2O5-ID) displayed higher molar ratios of Mn4+/Mn3+ and O-latt/O-ads, and better active oxygen desorption capacity, reducibility and larger specific surface, which promoted the preferable low-temperature catalytic oxidation of VOC. The increase in the content of Mn4+ on the surface of the Sm-Mn mullite reduced the surface defects and increased the proportion of its surface lattice oxygen, thereby promoting the attack of VOC molecules by more lattice oxygen. Combined with the analysis of reactant intermediate for benzene oxidation by in situ diffuse reflectance infrared Fourier transform spectroscopy, the catalytic mechanism of the catalyst was also explored. Moreover, SmMn2O5-ID also showed the excellent stability and the superior removal of mixed VOCs with different concentration ratios. This finding provides an efficient and practical method for exploiting highly active Mn-based mullite with a high efficiency and stability for the purification of air pollution. (C) 2020 Elsevier Inc. All rights reserved.